1. Field of the Invention
The present invention relates to an illuminating technique. More particularly, the present invention relates to a bar-like side-emitting light guide and a planar light source module constructed using a plurality of the bar-like side-emitting light guides.
2. Description of the Related Art
Beside a light source, most actual light source structures also include a light guiding structure, a dispersion plate and other optical components that guides the light from the light source into a light-emitting mode that fits the required function of the particular apparatus. For example, a planar light source is produced when a plurality of light emitting diodes are arranged together to form an original light source and the light emitted from these light emitting diodes are guided through a light guiding structure.
A planar light source has a variety of uses. For example, a planar light source can be used as a back light module in a planar display device. The light guiding structure can convert the light emitted from the light emitting diode (LED) into a planar form, covering a large area with the possibility of producing some light mixing effect. To convert the light emitted from the LED in the positive direction into side emitting light and produce the planar light effect, a conventional light guiding structure having a configuration as shown in FIG. 1 is used to surround the LED. As shown in FIG. 1, the conventional light guiding structure corresponds to the actual design of the LED. In fact, the LED is disposed at a center point F that passes through a central axis 43 of the light guiding structure. In the circularly symmetrical structure with respect to the central axis 43, a sharp protruding structure 102 and a bent base part 100 are disposed on each side of a cross-sectional plane. When the light guiding structure receives the light beam 104 emitted from the central point F, a portion of the light will be refracted by the base part 100 and the sharp protruding structure 102 and guided to the sides according to the incident locations. Then, as shown in FIG. 2, a plurality of the light guiding structures like the one in FIG. 1 is assembled together on a supporting bar 106. After that, a plurality of these supporting bars 106 are set up in parallel on a base plate 108 to form a conventional planar light source 108.
In the foregoing conventional light guiding structure, the design is for the disposition of singular light emitting diodes. The LED crystals are set up in such a way that the light from the LED is transformed to side emission through total reflection and refraction. However, if this type of LED package structure is used as the light source of a back light module, a large number of LED crystals and light guiding structures are required. As a result, the cost of producing a conventional planar light source is very high. Therefore, the manufacturers are seeking out other back light module designs having a lower production cost that still meet the required light emission quality.